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  • Articles  (323)
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  • 1
    Electronic Resource
    Electronic Resource
    Further Characterisation of the 91500 Zircon Crystal (2004)
    Oxford, UK : Blackwell Publishing Ltd
    Geostandards and geoanalytical research 28 (2004), S. 0 
    Details
    ISSN: 1751-908X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: This paper reports the results from a second characterisation of the 91500 zircon, including data from electron probe microanalysis, laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS), secondary ion mass spectrometry (SIMS) and laser fluorination analyses. The focus of this initiative was to establish the suitability of this large single zircon crystal for calibrating in situ analyses of the rare earth elements and oxygen isotopes, as well as to provide working values for key geochemical systems. In addition to extensive testing of the chemical and structural homogeneity of this sample, the occurrence of banding in 91500 in both backscattered electron and cathodoluminescence images is described in detail. Blind intercomparison data reported by both LA-ICP-MS and SIMS laboratories indicate that only small systematic differences exist between the data sets provided by these two techniques. Furthermore, the use of NIST SRM 610 glass as the calibrant for SIMS analyses was found to introduce little or no systematic error into the results for zircon. Based on both laser fluorination and SIMS data, zircon 91500 seems to be very well suited for calibrating in situ oxygen isotopic analyses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1751-908X.2004.tb01041.x
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  • 2
    Electronic Resource
    Electronic Resource
    The effect of surfaces and interfaces on the properties of thin film resistors in the CrSi/Al system
    Amsterdam : Elsevier
    Thin Solid Films 125 (1985), S. 321-327 
    Details
    ISSN: 0040-6090
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0040-6090(85)90239-1
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  • 3
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    Chrysoberyl-sillimanite association from the Roncadeira pegmatite, Borborema Province, Brazil: implications for gemstone exploration (2013)
    Czech Geological Society
    Details
    Publication Date: 2013-07-15
    Print ISSN: 1802-6222
    Electronic ISSN: 1803-1943
    Topics: Geosciences
    Published by Czech Geological Society
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  • 4
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    Quantification of water in majoritic garnet (2015)
    Mineralogical Society of America
    Details
    Publication Date: 2015-05-13
    Description: Majoritic garnet, characterized by an excess of silicon (〉3 Si per formula unit), is considered one of the major phases of the Earth’s transition zone from 410–660 km depth. Quantifying the H 2 O content of nominally anhydrous mantle minerals is necessary to evaluate their water storage capacity from experiments and modeling the Earth’s deep water cycle. We present mineral-specific infrared absorption coefficients for the purpose of quantifying the amount of water incorporated into majorite as hydroxyl point defects. A suite of majoritic garnet samples with varying proportions of Si, Fe, Al, Cr, and H 2 O was synthesized at conditions of 18–19 GPa and 1500–1800 °C. Single-crystals were characterized using X-ray diffraction, electron microprobe analysis, secondary ion mass spectrometry (SIMS), IR, Raman, and Mössbauer spectroscopy. We utilize SIMS and Raman spectroscopy in combination with IR spectroscopy to provide IR absorption coefficients for water in majoritic garnets with the general mineral formula (Mg,Fe) 3 (Si,Mg,Fe,Al,Cr) 2 [SiO 4 ] 3 . The IR absorption coefficient for majoritic garnet in the OH stretching region is frequency dependent and ranges from 10 470 ± 3100 Lmol –1 cm –2 to 23 400 ± 2300 Lmol –1 cm –2 .
    Print ISSN: 0003-004X
    Electronic ISSN: 1945-3027
    Topics: Geosciences
    Published by Mineralogical Society of America
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  • 5
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    Experimental formation of pyroxenite veins by reactions between olivine and Si, Al, Ca, Na, and Cl-rich fluids at 800 {o}C and 800 MPa: Implications for fluid metasomatism in the mantle wedge (2016)
    Mineralogical Society of America
    Details
    Publication Date: 2016-04-02
    Description: Fluids buffered by a plagioclase matrix are experimentally reacted with olivine megacrysts at 800 ºC and 800 MPa (piston-cylinder press, CaF 2 assembly) to form secondary veins of orthopyroxene ± clinopyroxene in the olivine. Fluids utilized were varied in both amount (0–2 wt%) and salinity (0–8 M NaCl). Assuming equilibrium with the plagioclase matrix, they are presumed enriched in Si, Al, Ca, Na, and Cl and are thereby similar in composition to slab-derived fluids. The experiments provide controlled, multi-component analogs of Si-metasomatism in the mantle wedge above subduction zones. The veins are dominated by orthopyroxene with minor clinopyroxene and form complex interconnected networks along fractures in the olivine. The reaction is rate limited by interfacial process of dissolution and precipitation. Porosity is developed throughout the veins and along sub-grain boundaries in the olivine megacrysts. These veins strongly resemble the textures observed in secondary metasomatic orthopyroxene veins widely reported in upper mantle xenoliths within arc magmas. A review of literature data on natural samples and experiments suggests that orthopyroxene ± clinopyroxene veins primarily form between 750–950 ºC and over a large pressure range from 0.8–3.4 GPa. The abundance and composition of these metasomatic veins may vary as a function of pressure, variances in the fluid-rock partition coefficients, and/or by modification of the metasomatic fluid during the reaction.
    Print ISSN: 0003-004X
    Electronic ISSN: 1945-3027
    Topics: Geosciences
    Published by Mineralogical Society of America
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  • 6
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    Special Collection: Advances in Ultrahigh-Pressure Metamorphism: Tetrahedral boron in natural and synthetic HP/UHP tourmaline: Evidence from Raman spectroscopy, EMPA, and single-crystal XRD (2016)
    Mineralogical Society of America
    Details
    Publication Date: 2016-01-05
    Description: Olenitic tourmaline with high amounts of tetrahedral B (up to 2.53 [4] B pfu) has been synthesized in a piston-cylinder press at 4.0 GPa, 700 °C, and a run duration of 9 days. Crystals are large enough (up to 30 x 150 μm) to allow for reliable and spatially resolved quantification of B by electron microprobe analysis (EMPA), single-crystal X-ray diffraction, and polarized single-crystal Raman spectroscopy. Tourmalines with radial acicular habit are zoned in [4] B-concentration [core: 2.53(25) [4] B pfu; rim: 1.43(15) [4] B pfu], whereas columnar crystals are chemically homogeneous [1.18(15) [4] B pfu]. An amount of 1.4(1) [4] B pfu was found in the columnar tourmaline by single-crystal structure refinement (SREF) ( R = 1.94%). The EMPA identify [T] Si –1 [V,W] O –1 [T] B 1 [V,W] (OH) 1 as the main and [X] –1 [T] Si –1 [X] Na 1 [T] B 1 as minor exchange vectors for [4] B-incorporation, which is supported by the SREF. Due to the restricted and well-defined variations in chemistry, Raman bands in the OH-stretching region (3000–3800 cm –1 ) are unambiguously assigned to a specific cation arrangement. We found the sum of the relative integrated intensity ( I rel ) of two low-frequency bands at 3284–3301 cm –1 (1) and 3367–3390 cm –1 (2) to positively correlate with the [4] B concentrations: [4] B [pfu] = 0.03(1) x [ I rel (1) + I rel (2)]. Hence, those bands correspond to configurations with mixed Si/B occupancy at the T site. Our semi-quantitative correlation also holds for well-characterized natural [4] B-bearing tourmaline from the Koralpe, Austria. This work shows the potential for Raman spectroscopy as a non-destructive method for the chemical classification of (precious) natural tourmaline, and as a tool to rapidly characterize chemical zonation of tourmalines in thin section.
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    Electronic ISSN: 1945-3027
    Topics: Geosciences
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  • 7
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    Distinctive properties of rock-forming blue quartz: inferences from a multi-analytical study of submicron mineral inclusions (2011)
    Mineralogical Society of Great Britain and Ireland
    Details
    Publication Date: 2011-08-30
    Description: The study discusses the mineralogical, geochemical and thermometric properties of rock-forming blue quartz from eight worldwide occurrences. Compared to non-blue quartz, blue quartz contains significant amounts of submicron-sized (1 {micro}m-100 nm) and nanometre-sized (
    Print ISSN: 0026-461X
    Electronic ISSN: 1471-8022
    Topics: Geosciences
    Published by Mineralogical Society of Great Britain and Ireland
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  • 8
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    Synthesis of K-dominant tourmaline (2014)
    Mineralogical Society of America
    Details
    Publication Date: 2014-02-15
    Description: K-dominant tourmaline was synthesized in the system MgO-Al 2 O 3 -B 2 O 3 -SiO 2 -KCl-H 2 O at 700 °C and 4.0 GPa. The crystals were zoned and characterized by less-potassic cores (1.46 wt% K 2 O) and more-potassic rims (up to 3.44 wt% K 2 O). The K-dominant tourmaline rims are represented by the average structural formula (K 0.60(3) 0.36(3) )(Mg 2.60(7) Al 0.40(7) )(Al 5.98(3) Si 0.02(3) )Si 6 O 18 (BO 3 ) 3 (OH) 3.92(7) O 0.08(8) , which is analogous to the structural formula of dravite and is referred to here as "K-dravite"; the maximum analyzed K content (3.44 wt% K 2 O) represents occupancy of the X site by 0.71 K pfu. The addition of Na to the system in approximately equal molar proportions to K results in the crystallization of K-bearing, Na-rich dravitic tourmaline, dramatically reducing the K content to an average value of 0.47 wt% K 2 O, corresponding to 0.10 K pfu. This suggests that a K-dominated bulk composition is necessary for K-dominant tourmaline crystallization. Compositional zoning shows that solid solution exists between end-member compositions of "K-dravite" [KMg 3 Al 6 Si 6 O 18 (BO 3 ) 3 (OH) 3 (OH)] and dravite via the isovalent exchange X K( X Na) –1 , magnesio-foitite via the coupled substitution X K Y Mg( X Y Al) –1 , and "K-olenite" via the coupled substitution Y MgOH( Y AlO) –1 . Structural refinement of the powder X-ray diffraction data provides a unit-cell volume for the synthesized "K-dravite" of 1580.1(5) Å 3 , which is greater than that determined for K-bearing dravitic tourmaline synthesized at the same conditions [1574.9(4) Å 3 ]. We interpret this to reflect expansion of the crystal structure due to incorporation of the relatively large K + ion.
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    Electronic ISSN: 1945-3027
    Topics: Geosciences
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  • 9
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    Ti- and Zr-minerals in calcite-dolomite marbles from the ultrahigh-pressure Kimi Complex, Rhodope mountains, Greece: Implications for the P-T evolution based on reaction textures, petrogenetic grids, and geothermobarometry (2014)
    Mineralogical Society of America
    Details
    Publication Date: 2014-07-02
    Description: Rutile, titanite, and zircon formed as relatively coarse-grained accessory minerals in several samples of high-grade calcite-dolomite marble with an early ultrahigh-pressure history. These minerals decomposed to a texturally complex set of secondary minerals during subsequent stages of retrograde metamorphism. The reactions involve several generations of geikielite-ilmenite as well as zirconolite [(Ca,Th,U)Zr(Ti,Fe,Nb,Ta) 2 O 7 ], kassite/cafetite [CaTi 2 O 4 (OH) 2 /CaTi 2 O 5 ·H 2 O], Ti-bearing humite group minerals, thorianite, and sometimes euxenite [(Ca,U,Th,REE)(Nb,Ta,Ti) 2 (O,OH) 6 ]. Stable coexistence of zircon and olivine is observed and stably coexisting titanite with olivine and/or humite-group minerals is reported here for the first time outside of carbonatites, kimberlites, or lamprophyres. Petrogenetic grids constructed for Ti- and Zr-bearing olivine/antigorite-saturated calcite-dolomite marbles show that geikielite is stable at highest pressures, followed by titanite and rutile, and that baddeleyite + diopside replaces zircon + calcite to higher pressures. The observed reaction textures are consistent with an earlier derived P-T path for the Kimi Complex. They corroborate a period of heating during decompression from 25 to 20 kbar and ca. 800 °C, where the assemblage olivine-diopside-spinel-rutile-zircon formed. This assemblage partially re-equilibrated during subsequent decompression and cooling, thus forming the observed reaction textures. Even though no memory of the UHP path is preserved in the accessory minerals, their reaction relationships turn out to be potentially very useful for geothermobarometry over a large range of metamorphic conditions.
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    Electronic ISSN: 1945-3027
    Topics: Geosciences
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  • 10
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    Diagenetic formation of interlayer-deficient fluorophlogopite as a clay mineral in Early Cambrian phosphorite (Lesser Himalaya, India): The trioctahedral analog of illite (2014)
    Mineralogical Society of America
    Details
    Publication Date: 2014-11-19
    Description: The occurrence of a trioctahedral analog of illite, the dioctahedral interlayer-deficient K-mica, has long been debated. Due to the inherent difficulties of determining structure and chemical composition of the extremely fine-grained material, earlier descriptions based on separated material are equivocal. Here we describe low-temperature (diagenetic) formation of fluorophlogopite, which is interlayer-deficient and therefore analogous to illite, using high-resolution in situ methods (transmission electron microscopy, TEM, with preparation by focused ion beam milling, combined with wavelength-dispersive analysis by field-emission gun electron microprobe). The average composition is K 0.5 Mg 2.8 V 0.01 Fe 0.005 [Si 3.15 Al 0.85 O 10 (OH) 0.65 F 1.35 ], including minor amounts of NH 4 for charge compensation as determined by electron energy loss spectroscopy. The K-deficient Mg-mica occurs in layer packages of ~10 layers, and no indications for interlayering with other sheet silicate layers such as chlorite or vermiculite could be identified with TEM. X-ray powder diffraction patterns of separated material confirm the absence of smectite components. The mineral was identified in phosphorites from the lowermost Cambrian Tal Group, Mussoori Syncline, Lesser Himalayas, India. The rocks are alternating phosphatic mudstones and phosphatic dolostones, at times interbedded with phosphate-poor carbonate layers, which are rich in organic matter. Sedimentary fluorophlogopite occurs in both rock types and in two textural associations; one in vesicles filled with amorphic organic matter, the other as reaction rims around illite, which contains up to 5 wt% V 2 O 3 in its rims. Textural arguments favor an early diagenetic formation of both, V-bearing illite and fluorophlogopite, closely associated with organic matter and linked to dolomitization. The high-F content stabilizes phlogopite to low temperatures. Our findings confirm that the stability field of fluorophlogopite extends from magmatic to metamorphic and sedimentary conditions.
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    Electronic ISSN: 1945-3027
    Topics: Geosciences
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